Implement build time optimizations

[sorvell]

In addition to polymer build and the polymer css build, there are a number of other possible build time optimizations that are worth exploring. Our current timeline is to invest in these features shortly after shipping version 2.0 of Polymer.

• strip whitespace
• pre-compile parsing of templates for bindings
• pre-compile polymer classes to include behaviors and property effects

[TimvdLippe]

Pre-building has been researched and a prototype is available at https://github.com/polymerlabs/loose-it Any further issues/improvements can be filed in that repository.